High strength aluminum alloy and its production method



HAJIME NAKAMURA ETAL 3,429,695

HIGH STRENGTH ALUMINUM ALLOY AND ITS PRODUCTION METHOD Filed June 15, 1966 Feb. 25, 1969 7 Sheet 222 HHH nnn va 3 3 6 G II 0000 n all G AAAA F 5. HGFE 2 0 l O O) 0 CB A mm A. .7 w ON 0 E m m m m r M .2 O 0 OE N T O m w m m m N 59. 8255 3523 E H O 0 0 0| 8 4 mwwzomdi wmwxo;

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INVENTORS HAJIME NAKAMURA et 0| BY Z r CONTENT ATTORNEYS United States Patent 3,429,695 HIGH STRENGTH ALUMINUM ALLOY AND ITS PRODUCTION METHOD Hajime Nakamura, Tokyo-to, Toshimitsu Hori, lVIatsudoshi, and Kazuo Sezaki, Tokyo-to, Japan, asslgnors to Ishikawajima-Harima Jukogyo Kabushiki Kaisha, Tokyo-to, Japan, a company of Japan Filed June 15, 1966, Ser. No. 557,816 Claims priority, application Japan, Oct. 12, 1965,

IO/62,557 US. Cl. 75-138 Int. c1. czzr 1/04; C22c 21/02 6 Claims ABSTRACT OF THE DISCLOSURE Thi invention relates to aluminum and its alloys possessing high tensile properties, and etiective and economical methods of production of these alloys.

The inventors have discovered that simultaneous additions of suitable amounts of zirconium and hydrogen to aluminum and its alloys greatly improve mechanical properties of the alloys, that heat-treatment of the alloys improves the mechanical properties very eflfectively, and that the mechanical properties of castings of the alloys can be further improved by hot-working. The inventors also have disclosed the mechanism responsible for the improvement of the mechanical properties of the alloys compared with commercial alloys of comparable chemical compositions to be due to the mutual interactions of aluminum, zirconium, and hydrogen in the alloys persisting even in alloys containing other alloying elements such as manganese, silicon, magnesium, nickel, copper and so on.

The aim of this invention is to obtain aluminum alloys possessing high tensile properties by utilizing the above mentioned phenomenon while limiting the amount of zirconium and hydrogen in the alloys. This invention relates to the aluminum alloys containing zirconium of 0.3 to 1.2%, hydrogen of 6 to 25 cc./10O g., aluminum as remainder, and incidental impurities, and the alloys containing one or more kinds of such alloying elements as 1.0 to 3.0% manganese, 0.1 to 1.5% silicon, 0.3 to 2.0% magnesium, 0.5 to 3.0% nickel, and 1.0 to 4.0% copper in addition to zirconium of 0.3 to 1.2%, hydrogen of 6 to 25 cc./ 100 g., aluminum as remainder and incidental impurities, and also relates to the methods of production of these aluminum alloys in conjunction for the improvement of the mechanical properties of the alloys.

The limitation for the zirconium content to the range of 0.3 to 1.2% in this invention has been set from the ground that the mechanical Properties of the alloys tend to decline as zirconium content was beyond the maximum value, and that the effect of zirconium on the improvement of mechanical properties is quite small when added below the minimum value.

In general, hydrogen has been thought to cause physical defects as blow-holes and pin-holes in ingots and castings if present in liquid aluminum alloys in appreciable amount, and prevention or elimination of hydro-gen from molten aluminum alloys to attain the hydrogen level of below 1 cc./ 100 g. is essentially important in practise.

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However, in this invention hydrogen is one of the indispensable alloying elements of the alloys, and is required to be present of the amount of 6 to 25 cc./ g. in the alloys. Even for an alloy with the hydrogen content of 25 cc./ 100 g, it is possible to be cast to sound ingots without causing any harmful defects such as blowholes and pin-holes due to hydrogen gas evolution when suitable amount of zirconium addition is made. In fact, hydrogen, contained in aluminum together with zirconium has been discovered to act to improve the mechanical properties of the alloys by the inventors. Although zirconium-bearing aluminum alloys containing hydrogen of below 6 cc./ 100 g. can be cast without causing any harmful defects to ingots, improvements of the mechanical properties are not appreciable. Because of the grounds given above, hydrogen content has been limited to the range of 6 to 25 cc./100 g.

Objects and advantages of this invention will be explained further from additional description and from the drawings.

FIGURE 1. Relationship between hydrogen content and Vickers hardness number of alloys of aluminum- 0.8% Zr-0.5% Si after heat-treatment at 400 C. for 2 hours.

FIGURE 2. Relationship between time for maximum Vickers hardness and heating temperature of alloys of aluminum-0.8% Zr, and aluminum-0.8% Zr-0.8% Si.

FIGURE 3. Relationship between maximum Vickers hardness and heating temperature of alloys of aluminum- 0.8% Zr-H and aluminum-0.8% Zr-0.8% Si-H FIGURE 4. Relationship between Vickers hardness and heating temperature of alloys of aluminum-0.8% Zr- 0.5% Si-H aluminum-0.8% Zr-0.5% Si-1.0% Mn-H aluminum-0.8% Zr-0.5% Si-2.0% Mil-H and aluminum- O.8% Zr-0.5% Si-3.0% Mn-H cooled after heat-treated for 2 hours at the temperatures.

FIGURE 5. Relationship between Vickers hardness and heating time at 400 C. of alloys of aluminum-0.8% Zr- 0.5% Si-H aluminum-0.8% Zr-0.5% Si-1.0% Mn-H and aluminum-0.8% Zr-0.5% Si-2.0% Mn-H FIGURE 6. Relationship between tensile strength and zirconium content of alloys of aluminum-0.5% Si-H aluminum-0.5% Si-l.0% Mn-H aluminum-0.5% Si- 2.0% Mn-H and aluminum-0.5% Si-3.0% Mn-H after heat-treatment in cast condition.

FIGURE 7. Relationship between tensile strength and zirconium content of alloys of FIGURE 6 after rolling at 400 C. with reduction of area of 55%.

FIGURE 8. Relationship between Vickers hardness and manganese and silicon content of alloys of basic composition of alumium-0.8% Zr-H after heat-treatment at 400 C. for two hours in cast condition.

FIGURE 9. Relationship between tensile strength and zirconium content of alloys of aluminum-0.5% Si-Zr-H 1.0% Ni after heat-treatment at 400 C. for two hours or hot-rolling at 400 C. with 55% reduction of area,

FIGURE 10. Relationship between tensile strength and zirconium content of alloys of aluminum-0.5% Si-Zr-H 2.0% Ni after heat-treatment at 400 C. for two hours or hot-rolling at 400 C. with 55% reduction of area.

FIGURE 1 is a graph showing the effect of varying the hydrogen content of a basic alloy composition such as 0.8% zirconium, 0.5% silicon, and aluminum as remainder on the hardness of permanent-mold castings after heat-treatment at 400 C. for two hours. From this data, it is apparent that alloys of the hydrogen content below 6 cc./100 g. have substantially weaker properties, and that those above 25 cc./ 100 g. appear to tend to diminish hardening. Hence, the hydrogen content of the range of 6 cc./100 g. to 25 cc./l00 g. is preferred.

FIGURE 2 is a graph showing the effect of varying the heat-treatment temperature on the time required to reach the maximum hardness of an alloy containing 0.8% zirconium and hydrogen (6 to 25 cc./100 g.), and an alloy of zirconium and hydrogen of the same amounts and silicon of 0.8%. Data shows that the addition of silicon to -an alloy of zirconium and hydrogen in aluminum accelerates the rate of hardening. For example, when annealed at 450 C., it takes 260 minutes for the siliconfree alloy to reach the maximum hardness, only 60 minutes for the silicon-bearing alloy. Hence, the addition of silicon as the third alloying element is effective in reducing heat-treatment time.

FIGURE 3 shows the effect of varying the heat-treatment temperature on the maximum hardness of the silicon-free and silicon-bearing alloys mentioned in FIG- URE 2. It is seen from the drawing that most preferable heat-treatment temperature for the maximum hardness is 400 C. in both cases, that heat-treatment below 400 C. yields unsaturated hardening during practical annealing time, that over-aging seems appearing at higher temperatures, and that the alloy containing silicon possesses higher maximum hardness than the silicon-free alloy.

FIGURE 4 shows the effect of varying the heat-treatment temperature on the hardness of cast alloys containing manganese as the third alloying element of the amount of 1.0 to 3.0%. Data shows that while the absolute value of hardness increases with increasing manganese content, heating at 400 C. yields the highest hardness regardless of the compositions of alloys as shown in previous data.

FIGURE 5 shows the effect of varying the heat-treatment time at 400 C. on the hardness of alloys mentioned in FIGURE 4. It is seen from the figure that with increasing manganese content, time for the maximum hardness decreases.

FIGURE 6 is a graph showing the effect of varying the zirconium content of a basic alloy composition as hydrogen to cc./100 g. and silicon 0.5% (example E), and of alloys with the identical amounts of hydrogen and silicon and varying the manganese contents of 1.0, 2,0, and 3.0% (Examples F, G, H respectively) On the tensile strength under as-cast condition and heat-treated condition. From this data, it is apparent that with the zirconium content of the range of 0.8 to 1.0%, the highest tensile strength results.

FIGURE 7 shows the same situation as in FIGURE 6 except for the specimen conditions, namely the alloys were rolled at 400 C. with the reduction of sectional area of 55%. It is also apparent from this data that tensile strength will increase with increasing the zirconium content and reach the maximum value at 0.8%, and decreasing with the zirconium content above the value. Exception is the case of an alloy containing 2% manganese where tensile strength lWill reach maximum with the zirconium content to 1.0% and decline thereafter. Hence, the practical range of the zirconium content is set to be from 0.3 to 1.2%.

FIGURE 8 is a graph showing the simultaneous variations in the contents of manganese and silicon on the hardness after heat-treatment for 2 hours at 400 C. The curves in the graph are equi-hardness lines and numbers in circles are hardness values. It is apparent from the graph that there exists interaction effect of manganese and silicon content on the hardness, and that the maximum hardness is obtained with the silicon content of 0.3 to 1.2%, 'and manganese of 2.0%, or nominally with 0.5% silicon and 2.0% manganese.

FIGURES 9 and 10 show the effect of varying the zirconium content on the tensile properties of alloys containing nickel as an alloying element. The alloys contain silicon of 0.5 zirconium of 0.3 to 1.0%, hydrogen of 6 to 25 cc./100 g., and nickel of 1.0 or 2.0% and are either heat-treated at 400 C. for two hours or hot-rolled at 400 C. with the reduction of area of 55%. From these data it is seen that the tensile strength of cast-state can be considerably increased by hot-rolling as in the previous cases. As for the effect of zirconium content, the tensile strength reaches maximum at about 1.0%, and then decreases with increasing the zirconium content in an alloy containing nickel of 1.0%. However, in cast alloys containing nickel of 2.0%, the maximum is with zirconium of 0.6%. From these data it is apparent that alloys containing nickel other than zirconium and hydrogen (6 to 25 cc./ g.) behave as similarly as the alloys explained above as for the effect of zirconium content.

The effect of addition of zirconium and hydrogen to several commercial aluminum alloys on the mechanical properties will be shown hereafter.

Table 1 shows the chemical compositions of two alloys one of which contains appreciable mount of hydrogen (Example K), and the other with small amount (Example L).

Table 2 shows the mechanical properties of these alloys after various treatments listed. From the table it is seen that although the hydrogen-bearing alloy exhibits higher tensile strength and hardness under as-cast condition, and being the effect of hydrogen-zirconium addition rather small, the effect becomes quite remarkable after heat-treatment at 400 C. for two hours and the tensile strength and the hardness increase almost twice as large as bfeore the heat-treatment, while decreasing the elongation slightly. The effect of hot-workin=g is also seen from the table as effective for the hydrogen-bearing 'alloy as increasing the tensile strength and the elongation markedly. It is seen from this example that suitable amounts of zirconium and hydrogen should be added simultaneously in order to increase the mechanical properties by heat-treatment.

Similar example is shown in Table 3 and Table 4. Table 3 shows the chemical compositions of alloys of aluminum with zirconium, manganese, silicon, and hydrogen. Table 4 shows the mechanical properties of these alloys after various heat-treatment listed. The treatments include ascast condition, heating at 400 C. for two hours, and hot-working at 400 C., and the mechanical properties are tensile strength, hardness, and elongation. An alloy containing hydrogen is labelled as example M, and one without hydrogen as N. From the results given, the effect of the addition of hydrogen is not so remarkable under as-cast condition as after heat-treatment at 400 C. for two hours. After the heat-treatment, the tensile strength and the hardness increase almost as twice as large while still retaining reasonable elongation. The effect of hotworking is again remarkable in increasing the tensile strength and especially the elogation. From these data it is seen that like the series of alloys of aluminum with zirconium and silicon, this series of aluminum alloys also can be strengthened through the suitable amount of hydrogen added through heat-treatment, and through hot-workmg.

Similar examples are given with a series of alloys of aluminum with copper, magnesium, and silicon, or name ly dur'alumin-type alloys. Table 5 shows the chemical compositions of these alloys: Examples P and R contain zirconium of 0.46% and 0.28% respectively and hydrogen of 15 to 20 cc./100 g. in addition to the normal alloyin-g elements, and Examples Q and S contain the same amounts of the alloying elements as Examples P and R respectively except for the hydrogen content which is in the order found generally in commercial aluminum alloys, or 1.5 to 2.0 cc./l00 g.

Table 6 shows the tensile strength, the hardness, and the elongation of these alloys after various treatments as follows: Treatment at, hot-rolling at 520 C. of the reduction of area of 55%, quenching to room temperature after keeping at 520 C. for 30 minutes, and aging at C. Treatment ,8, hot-rolling at 520 C. of 55% reduction, quenching to room temperature after keeping at 520 C. for 30 minutes, cold-rolling of 8% reduction, and aging at 165 C. Treatment 7, hot-rolling at 500 C. of 55 reduction, quenching to room temperature after keeping at 500 C. for 30 minutes, andaging treatment at TABLE 4.--MECHANICAL PROPERTIES OF ALUMINUM 165 C. Treatment 6, hot-rolling at 470 C. Of re- ALLOYS CONTAINING AND HYDROGEN duction, quenching to room temperature after keeping Mechanical properties 30 minutes at 470 C., and aging treatment at l165 C. T t W From the data shown in Table 6, it is apparent that reatmen fif 3 5, i sf alloys containing hydrogen of commercial level have the 5 -l fl) p c tensile strength of the range of 40 to 44 kg./mm. and Asmst condition, 45 kg./rnrn. for the cold-rolled case, and that the alloys $2 395}? i: of hydrogen level of 15 to 20 cc./ 100 g. have the tensile eamreatld fl 'j' 11$; strength of 45 to 50 ltg./mm. the upper value of WhlCh H fig i3 is with an alloy of zirconium of 0.46% and hydrogen of ,-5 '6f H E 1 yr 32.8 17 99 15 to cc./ 100 g. processed including cold rolling after 3 5 17. 9 43 54 quenching (treatment #3). It is seen again from these data Chemical compositions Zr Si Cu Fe H (cc./100 Al (percent) (percent) (percent) (percent) g). (percent) Example K O. 75 0. 16 O. 013 0. 04 18-22. Balance. L 0. 76 0. 10 0. 012 0. 02 2 D0.

TABLE 5.-CHElV IICAL COMPOSITION OF DURALUMIN-TYPE ALLOYS CONTAINING ZR AND HYDROGEN Chemical compositions Cu Mn Ni Mg Si Zr H (cc./ Al (percent) (percent) (percent) (percent) (percent) (percent) 100 g.) (percent) 3. 9O 2. 93 0. 95 0. 60 1. 0. 46 15-20 Balance. 3. 85 2. 95 0. 90 l]. 55 1. 50 0. 47 1. 5 D0. 3. 87 2. 93 0. 96 0v 51 1. 33 0. 28 14-19 Do. 3. 92 2. 90 O. 96 0. 55 1. 30 0. 29 2. 0 D0.

TABLE 6.MECHANICAL PROPERTIES OF DURALUMIN that the addltion of zirconium and hydrogen Increases the TYPE ALLOYS CONTAINING ZR AND HYDROGEN tensile strength of alumlnum alloys and even of duralumm- T u S ens'e tre th k .m type alloys. 0 Example 11g In) As seen with examples and descriptions, slmultaneous P Q R 5 addition of suitable amounts of zirconium and hydrogen 45 Treatment;

to aluminum alloys markedly increases the tensile 23-; 44 2 23.? 22.? strength and the hardness as well in cast condition as in 410 42 7 49.5 46.0 39 6 hot-worked condition.

TABLE 2.MECHANICA1 3 PROPERTIES OF ALUMINUM wh w 1 i i ALLOYS CONTAINING AND HYDROGEN 1. An aluminum base alloy having high tensile strength ec a properties and hardness and consisting essentially of by weight per- Treatment m 55 cent about 0.3 to 1.2% zirconium and hydrogen of about strength c 6 to 25 cc. at standard temperature and pressure per 10 0 (kg/mug) percent grams of the alloy, and the balance essentially aluminum As-cast condition: including incidental impurities.

iifigifi 5:111:3131111113133: 3:? i3 3? An aluminum base alley having high tensile strength and hardness and consisting essentially of by weight perisir a iii gi e 1%??? 2m mg 10 73 cent about 0.3 to 1.2% zirconium and hydrogen of about Example L 9-5 8 33 6 to 25 cc. at standard temperature and pressure per 100 Howomng (400 0 grams of the alloy, and at least one of about 1. 0 to 3.0% Example 3 8 25 78 manganese, about 0.1 to 1.5% silicon, about 0.3 to 2.0% Example 1.... 15 8 36 5s magnesium, about 0.5 to 3.0% nickel, or about 1.0 to

TABLE 3.-CHEMICAL COMPOSITIONS OF ALUMINUH ALLOYS CONTAINING Zr, Mn, Si, AND HYDROGEN Chemical compositions Zr Mn Si Fe Cu Hz(cc./l00 g.) Al (percent) (percent) (percent) (percent) (percent) (percent) Example:

M 0. 76 l. 0 0. 52 0. 03 0. 005 14-22 Balance. N 0.70 1. 0. 51 0.02 0. 004 1. 5 Do.

7 4.0% copper, and the balance essentially aluminum including incidental impurities.

3. A method of heat treating an aluminum alloy as claimed in claim 1 comprising heating said alloy in the temperature range of 350 C. to 450 C. for the time of 10 minutes to 48 hours, and subsequently cooling said alloy to room temperature by water-cooling, or oil-cooling, or air-cooling thereof.

4. A method of heat treating an aluminum alloy as claimed in claim 2 comprising heating said alloy in the temperature range of 350 C. to 450 C. for the time of 10 minutes to 48 hours, and subsequently cooling said alloy to room temperature by water-cooling, or oil-cooling, or air-cooling thereof.

5. A method of treating an aluminum base alloy, as claimed in claim 1 comprising hot Working the alloy in the temperature range of 400 C. to 500 C. and subsequently cooling the alloy by air-cooling or oil-cooling or water-cooling.

6. A'method of treating an aluminum base alloy, as claimed in claim 2 comprising hot working the alloy in the temperature range of 400 C. to 500 C. and subsequently cooling the alloy by air-cooling or oil cooling or water cooling.

References Cited UNITED STATES PATENTS 3,104,252 9/1965 Radd et a1. 75138 RICHARD O. DEAN, Primary Examiner.

US. Cl. X.R. 

